How Performance and Fate of Biodegradable Mulch Films are Impacted by Field Ageing

Three black biodegradable films based on PBAT-blends (PBAT/PLA, PBAT/PPC and PBAT/Starch) were tested for vine mulching in real field conditions. The impact of field ageing on their morphology, mechanical performance and ultimate biodegradation was investigated on films exposed at the soil surface or buried into the soil in order to assess the respective contribution of the main related ageing factors i.e. UV radiations and microorganisms. The fact that the soil-facing surface of films exhibited holes 18 months after installation suggested that the biodegradation process could occur above-soil even without previous burying step. However, the early loss of integrity of the biodegradable materials was attributed to UV radiations since beyond a certain threshold the photochemical modifications undergone by the material were too high to sustain its integrity. Whatever the material tested the deterioration of mechanical properties was correlated with the crosslinking of polymer chains inducing the formation of a gel fraction. Considering that the major part of the three materials studied is made of PBAT, the nature of the other polymer constituting the blend would not have a significant impact on the ageing mechanism of the material. Biodegradation analyses conducted in compost medium indicated that field ageing had a low impact on the percentages of mineralization whether the materials had been previously aged or not.